Saturable reactor for correcting raster distortion

ABSTRACT

A saturable reactor comprised of a cross-shaped core having a yoke on the center portion thereof and protrusions at right angles to the yoke and two coils wound on the yoke. Each coil of the said two coils is divided into two coil parts which are wound on the right and left yoke arms. The first pair of the said two coils is constituted so as to be identical as to the direction of the magnetic generation as is the pair of coils wound on the right and left yoke arms. The second pair of coils is constituted so as to be opposite to each other as to the direction of magnetic flux generation as is the pair of coils wound on the right and left yoke arms.

[ 1 Aug. 1, 1972 [54] SATURABLE REACTOR FOR CORRECTING RASTER DISTORTION[72] Inventor: Hiroshi Ikeuchi, Yokohama, Japan [73] Assignee: DenkiOnkyo Co., Ltd., Tokyo,

Japan [22] Filed: Aug. 20, 1970 [21] Appl. No.: 65,414

[30] Foreign Application Priority Data Aug. 25, 1969 Japan ..44/80574[52] US. Cl. ..335/227, 315/27 SR [51] Int. Cl ..H01f 7/06 [58] Field ofSearch ..335/210, 227, 297; 315/24, 315/27, 27 SR, 27 GD [56] ReferencesCited UNITED STATES PATENTS 3,571,606 3/1971 Kikuchi ..315/27SR3,329,861 4/1967 Barkowetal ..315/24 3,555,350 1/1971 Okuda ..315/24Primary Examiner-George Harris Att0rneyJames E. Armstrong and Ronald S.Cornell 5 7] ABSTRACT A saturable reactor comprised of a cross-shapedcore having a yoke on the center portion thereof and protrusions atright angles to the yoke and two coils wound on the yoke. Each coil ofthe said two coils is divided into two coil parts which are wound on theright and left yoke arms. The first pair of the said two coils isconstituted so as to be identical as to the direction of the magneticgeneration as is the pair of coils wound on the right and left yokearms. The second pair of coils is constituted so as to be opposite toeach other as to the direction of magnetic flux generation as is thepair of coils wound on the right and left yoke arms.

10 Claims, 14 Drawing Figures 774 I I ..1 a-

BACKGROUND OF THE INVENTION The present invention relates to a reactorfor controlling or modifying pincushion type distortion in cathode raytube displays. It is particularly well suited for use in conjunctionwith color display tubes.

Pincushion type distortion of cathode ray tube displays has long beenrecognized. In black-and-white displays, this type of distortion iscorrected to a considerable extent through the use of permanent magnets,which are so shaped and fixed in positions relative to the cathode as toproduce an appropriate magnetic biasing effect on the cathode ray beam.In the case of color display tubes, which are based on the use of shadowmask or similar principles, however, fixed correcting magnets cannot beused.

One approach, which has been adopted in connection with the correctionof pincushion distortion in color displays involves modulation orvariation of one of the sweep currents in such a manner as to producethe desired results.

In the arrangement for correction of raster distortion occurring in thevertical direction (e.g., top and bottom pincushion distortion), thecyclically varying vertical scanning current must be modulated at ahigher horizontal rate, such as by adding a horizontal rate correctioncurrent alternated parabolically to the vertical deflection current.

In the arrangement for the correction of raster distortion occurring inthe horizontal direction (e.g., side pincushion distortion), thecyclically varying horizontal scanning must be variedat a lower verticalrate, since the magnitude of a horizontal scanning must be varied at alower vertical rate, since the magnitude of a horizontal scanningcurrent is parabolical.

It has further been suggested in the prior art that this modulation beaccomplished electromagnetically using a combination of magnetic andelectrical circuitry which works on the principle of magneticsaturability.

In general, nominal correction can be produced by this means. There aremany kinds of saturable reactor device and circuit connections forcorrecting pincushion distortion such as those described in U.S. Pats.No. 2,906,919, No. 3,346,765, and No. 3,444,422.

The existing reactor, as seen in the aforementioned U.S. patents, iscomposed of a core that mutually couples the two ends of three parallelyokes, a coil is shuntwound on the two yokes on both sides of the saidcore in opposite winding direction and is connected in series, andanother coil is wound on the center of the said core. Since the verticaldeflection current has been applied to one of the above-mentioned coilsand the horizontal deflection current has been applied to the othercoil, the device has disadvantages as described herein.

In the manufacture of a reactor, coils are fitted to respective yokes ofan E-shaped core, and I-shaped cores are coupled on the free ends of theyokes of the E-shaped core in order to magnetically couple the yokes.Using this process, the manufacturing process has been time-consuming,making it unsuited to massproduction. Magnetic flux leakage has beensmall, since the yokes formed a closed magnetic path. However, sincecurrent magnetic flux density in the closed magnetic path variedmarkedly depending on the infinitesimal diflerences in the gaps in themagnetic path, the characteristics of individual products lostuniformity because of disparity in the gap arising in the coupled partof the E-shaped core and the l-shaped core.

The present invention offers saturable reactors extremely easy toassemble and manufacture and with uniform quality of individualproducts.

SUMMARY In accordance with the invention there is provided a saturablereactor for correcting raster distortion comprised of a cross-shapedmagnetic core having a yoke on the center portion thereof andprotrusions being provided at right angles thereto, and two coils woundon the said yoke, each coil of the said two coils being divided into twoparts and the divided coils wound on the respective arms formed on bothsides of the said protrusions, the first coil being so constituted thatthe magnetic fluxes generated in the two divided coil parts assume thesame direction when an electric current is caused to flow therethrough,while the said second coil is so constituted that the magnetic fluxeswill be generated in opposite directions in the two divided coil partswhen an electric current is caused to flow therethrough.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in detailin the accompanying drawings in which:

FIG. 1 is a longitudinal section of the reactor of the presentinvention.

FIG. 2 is a circuit diagram of the reactor shown in FIG. 1.

FIG. 3, 4, and 5 are longitudinal sections of front views of otherembodiments of the reactor of the present invention.

FIG. 6 is a side view of the reactor shown in FIG. 5

FIG. 7 is a longitudinal section of the front view of another embodimentof the reactor of the present invention.

FIG. 8 is a side view of the reactor shown in FIG. 7.

FIG. 9 is a longitudinal section of the front view of the reactor of thepresent invention.

FIG. 10 is a side view of the reactor shown in FIG. 9.

FIG. 11 is a longitudinal section of the front view of anotherembodiment of the reactor of the present invention.

FIG. 12 is an isometric of another embodiment of the reactor of thepresent invention.

FIG. 13 is a front view of the reactor shown in FIG. 12.

FIG. 14 is a circuit diagram of the reactor shown in FIG. 13.

DETAILED DESCRIPTION Referring to FIGS. 1 and 2 of the drawings, thereactor of the invention is composed of a cross-shaped core 10, a firstcoil 20 and a second coil 30 wound around the said core and fixedpermanent magnets 40 for magnetic biasing, which are attached to thecore mentioned above.

The core 10 of the reactor of the invention is a crossshaped core whichis composed of a piston-shaped yoke 11 and a protrusion 12 provided onthe middle of the yoke 11 so as to be at right angles to each other. Onthe right and left sides of the protrusion 12, the yoke l l farms arms11a and 11b partitioned off by protrusion Of the two coils mentionedabove, the first coil 20 is divided into two serially connected coilparts 21, 2], and each coil part 21, 21' is separately wound around theleft and right arms 11a, 11b of the yoke 11 mentioned above, thewindings being in the same direction.

Of the two coils mentioned above, the second coil 30 is divided into twoserially connected coil parts 31, 31, and each coil part 31, 31' isseparately wound around the left and right arms 11a, 11b of the yoke 11mentioned above on which the first coil is wound, the windings being inmutually opposite directions.

The first coil 20 and the second coil 30 are identical in use to thoseof the conventional reactor in that vertical deflection current iscaused to flow through one and the horizontal deflection current iscaused to flow through the other. This differs depending on whether thevertical distortion of the raster is to be corrected or the horizontaldistortion is to be corrected. In other words, it differs according tothe circuit to be connected to the reactor. And such circuits arealready publicly known through prior techniques, such as are detailed inthe aforementioned US. patents.

Such being the reactor of this invention, flow of horizontal deflectioncurrent Ih through the first coil 20 of vertical deflection current Ivthrough the second coil 30 induces and superimposes the reversecorrection current waveform of the horizontal deflection cycle on thevertical deflection current Iv. At the same time, since core ismagnetically biased by the permanent magnet 40, the amplitude of theaforementioned reverse correction current waveform becomes large at thebeginning and the end of the vertical scanning period and small at thecenter thereof. Also, since the coil parts 31, 31' of the second coil 30are wound so as to be in mutually reverse phases, the phase of thecorrection current waveform becomes reversed at the beginning and theend of the vertical scanning period.

When the basic waves only of the reverse correction current are takenout with a tuning circuit, sine wave current of forward correction,i.e., correction current of waveform that can be substituted for theapproximately parabolic current, is obtained. This allows correction ofthe vertical raster distortion. Since the operation and application ofthe reactor described in the foregoing are already publicly knownthrough prior techniques, detailed descriptions will be omitted.

As has been clarified by the foregoing descriptions and diagrams, thereactor related to the present invention uses the cross-shaped core 10,for the reason that it offers the advantage of easy fitting of the firstcoil and the second coil 30 on the arms 11a and 11b of the yoke l 1.Also, as the magnetic path is of the open type, it offers the advantageof the absence of any effect on the characteristics of individualproducts even when there are slight differences in the gaps between thearms of yoke 1 1.

Of course, in the open magnetic path, such as is the case with thereactor of the present invention, the magnetic flux leakage becomeslarge, but this disadvantage can easily be eliminated by providing amagnetic shield for the outer casing of the reactor.

Consequently, the reactor of this invention offers the benefits ofallowing mass production in a simple and facile manner and of uniformcharacteristics of individual products.

FIG. 3 and FIG. 4 show reactors where the protrusion 12 of core 10 hasan extension or extensions 12a arranged in parallel with yoke 11.

Extensions 12a are provided to narrow the gap on the magnetic path,reducing the leakage flux. This means has advantages in that it makespossible not only an increase in the amount of the flux current, butalso makes shielding of the flux easy.

Extensions 120 related to one embodiment according to the presentinvention may be equipped on only one end of the protrusion 12, asillustrated in FIG. 3, or may be equipped on both ends of protrusion 12,as illustrated in FIG. 4. When protrusion 12 is flangeshaped, it offersan advantage in that protrusion 12 can be made large in area FIG. 5 andFIG. 6 show a reactor in which an axially extending cavity 50 isprovided at the center of the yoke 11 of core 10. A piston-shaped barpermanent magnet 60, for a magnetic bias, magnetized in the axialdirection is slidably positioned within cavity 50. so as to be The saidreactor enables changing the magnetic bias of the right and left arms11a and 11b by sliding the bar permanent magnet 60, so that a rasterdistortion asymmetric in the top and bottom of the raster can becorrected by making the amplitude of a parabolic correcting currentasymmetric for the former and latter halves of a vertical scanningperiod.

It is known from the statement so far that the cores illustrated inFIGS. 1, 3, and 4 may be used for core 10. When the core shown in FIG. 1is used, the leakage flux can be reduced by constituting the said coreas mentioned below.

FIG. 7 and FIG. 8 illustrate the reactor cylindrical magnetic core whichis mounted on the crossshaped core 10 so that the inside surface of core70 will contact the ends of the yoke protrusions. It is desirable forthe said reactor that yoke protrusion 12 is flangeshaped becausecylindrical core 70 is mounted on the core 10 in parallel with yoke 11.

This type of reactor mentioned above also offers the advantage that themagnetic resistances between the arms 11a and 11b of the yoke andcylindrical core 70 can be relatively increased or decreased by slidingthe cylindrical core 70 along yoke l 1.

FIG. 9 and FIG. 10 show a reactor in which a permanent bar magnet 60 isinserted into the core 10 illustrated in FIGS. 5 or 7.

The operating characteristics of the reactor related to theabove-mentioned embodiment will be clearly known from the statement sofar.

Consequently, it is desirable for the reactors shown in FIGS. 5, 7, and9 that a core strip is mounted on both ends of the core 10 of eachreactor. This means offers the advantages that the gap between the yokearms 11a and 11b of the yoke 11 and the yoke protrusion 12 can not onlybe made narrower, but also coils 20 and 30 can be held with core strip80.

However, since the reactor according to this invention is devised so asto eliminate the characteristic change due to small variation of the gapwith the open magnetic path formed in the magnetic circuit. it isnecessary for a reactor of type in FIG. 7 to determine the size of corestrip 80 and the length of cylindrical core 70 so that the gap betweenis not too narrow.

FIG. 11 illustrates a reactor in which a core strip 90 is mounted onprotrusion 12 of core 10.

Core 10, according to the embodiment of FIG. 1 l, is not flange-shapedusually, so that a pair of protrusions 12 and 12' are stuck out inopposite directions to each other on the middle of the yoke l 1.

Core strip 90 is arranged on one protrusion 12 so as to be in parallelwith the said yoke 11 and is attached to on the protrusion 12 so as toslide along the yoke in parallel.

In this embodiment according to this invention, since it is possible tochange the gap between arm 11a and protrusion 12 and the gap between arm11b and protrusion 12 by sliding the said core strip 90, the magneticbias prints of arms 11a and 11b can be changed. Therefore, a fixedpermanent magnet 40, as illustrated in FIG. 1, is often used as the biasmagnet. In this case, a bar magnet as illustrated in FIG. 5 may be usedfor a particular purpose.

FIG. 12 to FIG. I4 show a reactor in which a U- shaped permanent magnet100 is placed on the said core 10 to be used as the bias magnet.

Permanent magnet 100 having magnetic poles at both ends is mounted oncore 10 in such a manner that both magnetic poles are attached to theexternal surface of core 10 so that the magnetic poles may be placed onthe external surfaces of the arms on the free ends outside the windingparts of coils and 30. That is, coils 20 and 30 are positioned in thespace of the U- shaped permanent magnet.

The reactor relating to the above-mentioned embodiment is devised sothat permanent magnet 100 can he slid to bring one magnet pole S closeto the coils 20 and 30, thus enabling it to separate the other magnetpole N from the coils; therefore, the magnetic bias points of the arms11a and 11b be asymmetrically changed and, also, both arms 11a and 11bcan be identical in the magnetic bias point by making equal thedistances between both magnetic poles and the coils.

Consequently, the reactor according to the abovementioned embodiment,like the reactor shown in FIG. 5, can be used for correcting thevertical distortion of the raster whether it is symmetrical or not.

While a few embodiments of this invention have been illustrated anddescribed in detail, it is particularly understood that this inventionis not limited thereto or thereby. For example, the reactor shown inFIG. 12 may use the cores shown in FIGS. 3 and 4, or the core shown inFIG. 1 may be mounted with the cylindrical core shown in FIG. 7.

What is claimed is:

l. A saturable reactor for correcting raster distortion comprised of across-shaped magnetic core consisting essentially of a central yokeportion and a divider portion in the fonn of a protrusion intersectingthe central portion at a right angle and extending to the opposite sidethereof, thereby dividing the central yoke portion into separate armportions and forming a magnetic core which is cross-shaped when viewedin cross-section, and two coils wound on the yoke portion, each of saidc '15 bei s bdivided' t arts d the th d'- vi ed coiigbeing woun br? diispectiiiia arm poi t ron s fonned on both sides of the protrusion, thefirst coil being so constituted that the magnetic fluxes generated inthe two divided coil parts assume the same direction when an electriccurrent is caused to flow therethrough, while the said second coil is soconstituted that the magnetic fluxes will be generated in oppositedirections in the two divided coil parts when an electric current iscaused to flow therethrough, and wherein the core is so structured thatthe cross-sectional dimensions are identical along its entire length,with no projections appurtenant to the respective ends thereof.

2. A saturable reactor for correcting raster distortion according toclaim 1, wherein at least one end of the protrusion is extended in adirection parallel to the central yoke.

3. A saturable reactor for correcting raster distortion according toclaim 1, wherein the protrusion consists of two oppositely positionedprojections.

4. A saturable reactor for correcting raster distortion according toclaim 1, wherein the protrusion consists of a continuous discsurrounding the yoke portion.

5. A saturable reactor for correcting raster distortion according toclaim 1, wherein a cylindrical core is mounted on the cross-shaped corewith the inside wall of the cylindrical core in slidable contact withsaid divider portion of the cross-shaped core.

6. A saturable reactor for correcting raster distortion according toclaim 2, wherein the protrusion is extended by attaching thereto corestrips in parallel with the central yoke.

7. A saturable reactor for correcting raster distortion according toclaim 1, wherein a U-shaped permanent magnet having magnetic poles atboth ends is mounted on the cross-shaped core so that the said magneticpoles contact the right and left arm portions of the yoke respectively,and wherein the coils are positioned within the magnetic poles.

8. A saturable reactor for correcting raster distortion according toclaim 1, wherein permanent magnets for bias are mounted on both ends ofthe yoke.

9. A saturable reactor for correcting raster distortion according toclaim 1, wherein a cavity is provided in the center of the yoke in theaxial direction thereof and a permanent bar magnet magnetized in theaxial direction thereof is movably inserted into the cavity.

10. A saturable reactor for correcting raster distortion according toclaim 9, wherein core strips are placed on both ends of the yoke.

Il l

1. A saturable reactor for correcting raster distortion comprised of across-shaped magnetic core consisting essentially of a central yokeportion and a divider portion in the form of a protrusion intersectingthe central portion at a right angle and extending to the opposite sidethereof, thereby dividing the central yoke portion into separate armportions and forming a magnetic core which is cross-shaped when viewedin cross-section, and two coils wound on the yoke portion, each of saidcoils being subdivided into two parts and the thus divided coils beingwound on the respective arm portions formed on both sides of theprotrusion, the first coil being so constituted that the magnetic fluxesgenerated in the two divided coil parts assume the same direction whenan electric current is caused to flow therethrough, while the saidsecond coil is so constituted that the magnetic fluxes will be generatedin opposite directions in the two divided coil parts when an electriccurrent is caused to flow therethrough, and wherein the core is sostructured that the cross-sectional dimensions are identical along itsentire length, with no projections appurtenant to the respective endsthereof.
 2. A saturable reactor for correcting raster distortionaccording to claim 1, wherein at least one end of the protrusion isextended in a direction parallel to the central yoke.
 3. A saturablereactor for correcting raster distortion according to claim 1, whereinthe protrusion consists of two oppositely positioned projections.
 4. Asaturable reactor for correcting raster distortion according to claim 1,wherein the protrusion consists of a continuous disc surrounding theyoke portion.
 5. A saturable reactor for correcting raster distortionaccording to claim 1, wherein a cylindrical core is mounted on thecross-shaped core with the inside wall of the cylindrical core inslidable contact with said divider portion of the cross-shaped core. 6.A saturable reactor for correcting raster distortion according to claim2, wherein the protrusion is extended by attaching thereto core stripsin parallel with the central yoke.
 7. A saturable reactor for correctingraster distortion according to claim 1, wherein a U-shaped permanentmagnet having magnetic poles at both ends is mounted on the cross-shapedcore so that the said magnetic poles contact the right and left armportions of the yoke respectively, and wherein the coils are positionedwithin the magnetic poles.
 8. A saturable reactor for correcting rasterdistortion according to claim 1, wherein permanent magnets for bias aremounted on both ends of the yoke.
 9. A saturable reactor for correctingraster distortion according to claim 1, wherein a cavity is provided inthe center of the yoke in the axial direction thereof and a permanentbar magnet magnetized in the axial direction thereof is movably insertedinto the cavity.
 10. A saturable reactor for correcting rasterdistortion according to claim 9, wherein core strips are placed on bothends of the yoke.